The colored crystals used during the summoning ritual in Sloobludop were most likely Sapphires.
There are likely breaks in the Demonweb Pits. This would need to be the case in order for the Demon Princes to escape into the underdark so easily. If the Demonweb Pits are broken, there is likely an issue with Lolth, for she is fated to maintain the webs.
Spider King (Below Gracklstugh):
Acquired: 10x Sending stone things. All connected to each other. Basically magic walkie-talkies.
Society of Brilliance:
Acquired: Map to Glacier temple on the surface where you can forge a Sunblade. (Skris can give additional directions)
Acquired: Panaceum Root (from spellcasting foci bag) (from Nirac) (Spellcasting component for low-level revive spells)
Acquired: Self-sustaining goldfish-in-a-ball
Before Demonweb Pits:
Library of Gravenhollow:
Best bet to escape the Underdark: